Re: [PATCH] scsi: mpt3sas: fix hang on ata passthru commands

[Jason Baron]

On 01/01/2017 12:39 PM, James Bottomley wrote:
> On Sun, 2017-01-01 at 11:33 -0500, David Miller wrote:
> > From: Bart Van Assche <Bart.VanAssche@xxxxxxxxxxx>
> > Date: Sun, 1 Jan 2017 14:22:11 +0000
> >
> > > My recommendation is to revert commit 18f6084a989b ("scsi: mpt3sas: Fix
> > > secure erase premature termination"). Since the mpt3sas driver uses the
> > > single-queue approach and since the SCSI core unlocks the block layer
> > > request queue lock before the .queuecommand callback function is called,
> > > multiple threads can execute that callback function (scsih_qcmd() in this
> > > case) simultaneously. This means that using scsi_internal_device_block()
> > > from inside .queuecommand to serialize SCSI command execution is wrong.
> >
> > But this causes a regression for the thing being fixed by that
> > commit.
>
> Right, we don't do that; that's why I didn't list it as one of the
> options.
>
> > Why don't we figure out what that semantics that commit was trying to
> > achieve and implement that properly?
>
> Now that I look at the reviews, each of the reviewers said what the
> correct thing to do was: return SAM_STAT_BUSY if SATL commands are
> outstanding like the spec says.  You all get negative brownie points
> for not insisting on a rework.
>
> Does this patch (compile tested only) fix the problems for everyone?

Hi,

Yes, with this patch applied my system boots :)

...

> @@ -4083,6 +4077,16 @@ scsih_qcmd(struct Scsi_Host *shost, struct scsi_cmnd *scmd)
>  		return 0;
>  	}
>
> +	/*
> +	 * Bug work around for firmware SATL handling
> +	 */
> +	if (sas_device_priv_data->ata_command_pending) {
> +		scmd->result = SAM_STAT_BUSY;
> +		scmd->scsi_done(scmd);
> +		return 0;
> +	}
> +	set_satl_pending(scmd, true);
> +
>  	sas_target_priv_data = sas_device_priv_data->sas_target;
>
>  	/* invalid device handle */


I was also wondering if 2 threads could both fall through and do:
'set_satl_pending(scmd, true)'; ?

Afaict there is nothing preventing that race?

Thanks,

-Jason